chore: Move `Invertible`

[YaelDillies]

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Move the material about Invertible to files under Algebra.Group, Algebra.GroupWithZero, Algebra.Ring.

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[github-actions[bot]]

🚀 Pull request has been placed on the maintainer queue by Ruben-VandeVelde.

[github-actions[bot]]

No declarations were harmed in the making of this PR! 🐙

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You can run this locally as follows

## summary with just the declaration names:
./scripts/no_lost_declarations.sh short <optional_commit>

## more verbose report:
./scripts/no_lost_declarations.sh <optional_commit>

[jcommelin]

bors r+

[mathlib-bors[bot]]

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[sgouezel]

bors r+

[mathlib-bors[bot]]

Pull request successfully merged into master.

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